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Biomedical subjects

W D Christensen

Publications and source records attributed to W D Christensen.

7 recordsLinked to original sources
PubMed1986

Aerosol deposition and flow limitation in a compliant tube.

Studies in intact dogs have suggested that aerosol deposition is enhanced in the proximity of a flow-limiting segment (FLS) formed during cough. The mechanism for that observation was investigated using a monodisperse (geometric SD less than or equal to 1.15) fluorescent aerosol produced in a condensation generator. The aerosol was passed through a compliant tube (Penrose) that had been mounted vertically in a two-chamber box. The surrounding pressure (Ps) in the upstream chamber was controlled independent of the surrounding pressure in the downstream chamber, thus allowing development of an FLS near the exit of the upstream chamber. At fixed inlet pressure (P1) and Ps, flow limitation was achieved over a range of 0.1-0.5 l X s-1 by lowering downstream pressure alone (P2). The influence of the FLS cross-sectional geometry on the site of peak deposition was examined because area of an FLS is a function of transmural pressure (Ptm = Px - Ps). For those constriction geometries that did not involve opposing wall contact, the deposition distribution was characterized by a single peak immediately downstream of the constriction. In the most compressed geometries the peak in deposition was diminished and shifted further downstream. Total aerosol deposition was found to be characterized by a dimensionless particle inertia parameter formed as the ratio of particle stopping distance and the minor radius of the elliptical tube cross section. The deposition of small particles with an inertial parameter less than 0.01 was found to be independent of geometry and constriction velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1985

Occupational exposure to cancer chemotherapeutic drugs: a literature review.

Chemotherapeutic drugs are frequently used in cancer treatment. The mutagenic and carcinogenic potential of many antineoplastic agents has been well established. Clinical personnel may be occupationally exposed to antineoplastic agents during the preparation, administration or disposal procedures. This article provides a brief review of the current literature in medical, pharmacy and nursing journals concerning chemotherapeutic drugs. Its purpose is to increase industrial hygienists' awareness of the need for exposure control. Consensus recommendations on handling procedures published by the National Study Commission on Cytotoxic Exposure are included in the Appendix.

Antineoplastic Agents↗
PubMed1981

Industrial hygiene and the F-16 air combat fighter.

This paper describes a program of mutual cooperation between a defense contractor and the line and medical service of the USAF in controlling potential exposures to hydrazine as it is used on the F-16 aircraft. The early involvement of USAF industrial hygienists in the evaluation of exposures to hydrazine during various maintenance activities is described. These efforts have led to an engineering design concept which emphasizes control of exposure and minimizing the potential for accidental exposure. Recognizing that the risk of an accidental exposure will never be reduced to zero, the USAF Medical Service has implemented a comprehensive program of medical surveillance and health education directed towards the work force responsible for maintenance of the F-16 hydrazine system.

Aircraft↗
PubMed1978

The effect of probe bluntness on sampling particulates from calm air.

The size-selective characteristics of circular inlets as a function of bluntness was examined using polydisperse spherical glass beads. Four levels of bluntness (0.5, 1, 5, and 50) and three sampling velocities (4, 20, and 40 cm/sec) were studied. Particle count and weight percent distributions were determined using a 15-channel electronic counter. At a sampling velocity of 40 cm/sec the weight percent distributions shifted toward particles of larger diameters with increasing bluntness. Little or no effect was discerned at sampling velocities of 20 and 4 cm/sec. As the velocity increased from 4 to 40 cm/sec at constant bluntness, the weight percent distributions shifted away from larger diameter particles. The results suggest that at some sampling conditions probe bluntness may be a variable which deserves consideration in particulate sampling.

Aerosols↗
PubMed1978

Evidence for quantitative variability of bacterial opsonic requirements.

We studied human serum opsonins by using combinations of heat inactivation and chelation to inhibit complement, adsorption to remove antibody, and trypan blue to inactivate the C3 receptor of human polymorphonuclear leukocytes. Streptococcus pneumoniae, serotype 25, required both complement and immunoglobulin for opsonization, even though that strain activated the alternative complement pathway. Both strains of Escherichia coli required antibody and complement, but varied in the degree of dependence on the C3 opsonin, since trypan blue moderately inhibited the killing of E. coli-1 and markedly inhibited the killing of E. coli-2. Serratia marcescens was opsonized in heat-inactivated serum (limited complement) or serum absorbed at 0 degrees C with S. marcescens (limited antibody), but depended on the C3 receptor in absorbed serum. S. marcescens activated the alternative pathway. Thus, opsonic requirements varied with the availability of opsonins. Requirements for bacterial opsonization vary with species and strains within species, perhaps reflecting quantitative relationships among alternative and classical pathway activation of C3, efficiency of adsorption of C3 or immunoglobulin G to bacterial surfaces, and efficiency of attachment of these ligands to polymorphonuclear leukocyte receptors. Furthermore, although not always sufficient for opsonization, the C3 opsonin (activated through either the classical or alternative pathway) appears necessary for effective phagocytosis and killing of all strains studied.

Antibodies, Bacterial↗
PubMed1978

Trypan blue inhibits complement-mediated phagocytosis by human polymorphonuclear leukocytes.

Trypan blue completely inhibited attachment of human polymorphonuclear leukocytes (PMN) to Sepharose beads coated with C3 ant to sheep erythrocytes coated with IgM plus C3, but it did not inhibit attachment to erythrocytes coated with IgG. These results suggested that trypan blue inhibited C-mediated attachment to PMN membranes. Corroborative studies were performed with a strain of Staphylococcus aureus that requires C but not antibody, for opsonization and that activates the alternative pathway. Trypan blue was not toxic to PMN or bacteria, did nto interfere with immunoglobulin or C interactions, and did not affect attachment of opsonins to bacteria. However, the dye impaired PMN killing of S. aureus in normal nonimmune serum by inhibiting bacterial attachment to and ingestion by PMN. Further evidence that the inhibition was at the C3 receptor level came from the observations that, 1) once staphylococci were attached to PMN at either 37 degrees C or 0 degrees C, addition of trypan blue did not inhibit killing; and 2) trypan blue inhibited killing of bacteria opsonized with serum sufficient in C but previously absorbed at 0 degrees C with the same strain of organism to deplete specific antibody. Further studies with this agent may elucidate the roles of opsonic receptors on human phagocytes.

Cell Adhesion↗